Screen printing machine with transport band for temporarily adhesively securing web during printing

ABSTRACT

A screen printing machine, especially a rotary screen printing machine, which is of the type wherein the material to be printed upon is delivered to a transport band and by the addition of heat and pressure is temporarily secured by means of a thermoplastic adhesive carried by the transport band to such transport band, until the material, after passing the color applying mechanism, is removed from the transport band so as to undergo further treatment. According to an important aspect of the invention, a heat source is arranged over a partial length of the transport band coated with the thermoplastic adhesive, this heat source being situated forwardly of the contact location of the material to be printed upon and the transport band.

Unite States aet Thierstein 154] SCREEN PRINTING MACHINE WITH TRANSPORT BAND FOR TEMPORARILY ADHESIVELY SECURING WEB DURING PRINTING [72] Inventor: Hans Thierstein, Holzacker, Switzerland [73] Assignee: Fritz Buser AG Maschinenfabrik,

Wiler by Utzenstorf, Switzerland 22] Filed: April 27, 1970 [21] Appl.No.: 32,123

[30] Foreign Application Priority Data May 2, 1969 Switzerland ..6749/69 [52] US. Cl ..101/1l8, 101/228 [51] Int. Cl. ..B4lf 13/02 [58] Field of Search ..lO1/ll5,116,176,178,

[4 1 Oct. 24, 1972 3,237,314 3/1966 Smith, Jr. 101/416 2,565,570 8/1951 Messinger....10l/4l6.1 A UX 3,038,833 6/1962 Glover ..156/322 3,364,091 1/1968 Conti ..156/320 X 3,316,137 4/1967 Wisotzky 156/222 FOREIGN PATENTS OR APPLICATIONS 1,132,532 .7/1962 Germany ..10l/181 155,820 3/1954 Australia 101/1 15 345,458 5/1960 Switzerland ..156/322 Primary Examiner-J. Reed Fisher Attorney-Werner W. Kleeman [5 7] ABSTRACT A screen printing machine, especially a rotary screen printing machine, which is of the type wherein the material to be printed upon is delivered to a transport band and by the addition of heat and pressure is temporarily secured by means of a thermoplastic adhesive carried by the transport band to such transport band, until the material, after passing the color applying mechanism, is removed from the transport band so as to undergo further treatment. According to an important aspect of the invention, a heat source is arranged over a partial length of the transport band coated with the thermoplastic adhesive, this heat source being situated forwardly of the contact location of the material to be printed upon and the transport band.

4 Claims, 2 Drawing Figures PATENTED 0m 24 1912 PRIOR ART Fig.1

INVENT OR BY M 40.

ATTORNEY SCREEN PRINTING MACHINE WITH TRANSPORT BAND FOR TEMPORARILY ADHESIVELY SECURING WEB DURING PRINTING BACKGROUND OF THE INVENTION The present invention relates to an improved screen or film printing machine, especially a rotary screen printing machine, wherein the material to be printed upon is delivered to a transport band and through the addition of heat and pressure is temporarily secured by means of a thermoplastic adhesive applied to the transport band to the latter, until the material, after passing the printing or coloring mechanism, is removed from the transport band for further treatment.

Screen printing machines wherein the material to be printed upon is secured with the aid of a thermoplastic material to the printing blanket or the transport band are already well known to the art. One such type apparatus has been disclosed in the commonly assigned, copending Unites States application, Ser. No. 11,463, filed Feb. 16, 1970, now US. Pat. No. 3,601,299 of Richard Murer and Herman Leiser, entitled Continuv ously Operating Thermoplastic Adhesive Apparatus, Preferably for Printing Purposes.

The thermoplastic materials can, for instance, contain a plasticizer in order to maintain a sufi'icient adhesiveness during a certain period of time. During practical operation of this type equipment, the thermoplastic adhesive which is located upon the transport band, together with the material to be printed upon, is heated up, and thereafter, the material is secured to the transport band through the action of a pressure roller exerting a pressure force. Now the adherence of the material to the transport band should be great enough so that during advance of the transport band no relative displacement occurs between this material to be printed upon and the transport band. Yet, on the other hand, the adherence of the material, after passing through the film or screen printing machine, should be capable of being pulled off of the transport band without application of excessive force and delivered for further processing.

There are also known to the art further screen printing machines in which the attachment of the material to be printed upon has been improved in that, the material is pressed onto the transport band, so that the pressure is controlled as a function of the quality of the material to be printed upon and the transport or feed velocity.

A further improvement of the thermoplastic-adhesive bonding technique heretofore considered is achieved in that the roller insuring for the heating up of the adhesive material and exerting the pressure force is constructed to be relatively displaceable with respect to the rollers of the transport band. Consequently, there can be attained a further uniformity of the heating of the material and the adhesive.

The known techniques for securing the material to be printed upon to the transport band and the apparatus structures which have been devised in this connection have proven themselves in actual practice. Yet, experience has shown that the known apparatuses are associated with certain limitations insofar as, on the one hand, concerns the production speed and, on the other hand, the use of certain heavy fabric qualities.

SUMMARY OF THE INVENTION Therefore, a need exists for a screen printing machine which is capable of coping with these limitations in an effective manner. The present inventive screen printing machine therefore has for one of its primary objectives to provide such type equipment which does just that.

Another, more specific object of the present invention relates to an improved screen printing machine which eliminates the aforementioned limitations of the known screen printing machines.

A further, more specific object of the present invention relates to an improved screen printing machine which enables both an increase of the production speed as well as also the use of heavy fabric qualities.

Now, in order to implement these and still further objects of the invention, which will become more readily apparent as the description proceeds, the inventive screen printing machine is manifested by the features that a heat source is arranged over a partial length of the transport band covered with the thermoplastic adhesive, and this heat source is disposed before the contact location of the material to be printed upon with the transport band.

According to one aspect of the invention, the heat source is advantageously arranged before a pair of rollers which secure the material to be printed upon, delivered past the heat source, to the transport band by a pressing operation. The heat source can preferably consist of a number of adjacently arranged heat radiating elements, wherein the radiant heat which is radiated upwardly is at least partially screened by means of a suitable cover member or shield along the surface of which there is guided the material to be printed upon. However, for certain applications it is also possible to guide the material to be printed upon below the heat source and to deliver such material to the pair of rollers.

According to a further aspect of the invention, the heat radiating elements together with their cover or shield are advantageously capable of being raised for the purpose of interrupting the heating of the transport band. In so doing, it is of advantage if the cover or shield is mounted to be pivotable about an axis extending parallel to the axes of the rollers and arranged at the region of such pair of rollers. Furthermore, during raising of the cover or shield it is possible to also advantageously undertake the lowering of the roller situated beneath the transport band, so that the heat radiating elements collectively, in groups, or individually can be switched on and switched 0E.

BRIEF DESCRIPTION OF THE DRAWING The invention will be better understood and objects other than those set forth above, will become apparent when consideration is given to the following detailed descriptionthereof. Such description makes reference to the annexed drawing wherein:

FIG. 1 schematically illustrates a known technique for securing the material to be printed upon with the aid of a thermoplastic adhesive to the transport band of a film or screen printing machine; and

FIG. 2 schematically illustrates a portion of the film or screen printing machine designed according to the teachings of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Describing now the drawing, in FIG. 1, by means of which there will be explained the known technique for the temporary attachment of the material to be printed upon with the transport band during the printing operation, it will be observed that reference numeral 1 designates the transport band coated with a suitable thermoplastic adhesive, for instance of the type disclosed in the heretofore mentioned copending application of the assignee of this invention. This transport band 1, serving as a carrier, passes between a pair of rollers 2 and 3, consisting of a heated pressure roller 2 and a counterroller 3, for instance formed of rubber.

The material 4 to be printed upon is guided with a predetermined angle a about the heated pressure roller 2 and thereafter is conducted to the transport band 1. During the contact time of the material 4 with the heated pressure roller 2, defined by the angle a,- the aforementioned material 4 is preheated. So that the thermoplastic adhesive at the transport band 1 will be heated, the heat must pass through the material 4. It is therefore understandable that this indirect heating of the transport band 1 is then disadvantageous if, in so doing, heating of the transport band 1 is noticeably retarded. In the case of thick fabrics and certain synthetic materials, possessing good insulation properties, this can result in such a drawback that it is impossible to obtain sufficient heat for the temporary attachment with the transport band 1, specifically the thermoplastic adhesive located thereon. In addition thereto, it should be understood that with increased conveying speed of the material 4 the contact or residence time of this material at the contact or pressure roller 2 and also the heating time for the transport band 1 is so short that a reliable attachment of the material 4 to be printed upon with the transport band 1 is no longer possible when exceeding a predetermined upper speed limit of the material.

Now, in FIG. 2 there is schematically illustrated those components of the inventive screen printing machine which are necessary for a complete understanding of the inventive concepts, and specifically those components partaking in the delivery of the material 12 to be printed upon and the attachment thereof with the transport band 14. This portion of the machine, also known as the infeed stand 10, is arranged forwardly, with respect to the feed direction, of the coloring or printing mechanisms, such as the illustrated printing device 11. FIG. 2 is specifically concerned with a rotary screen printing machine, wherein the first printing or coloring mechanism 11 is shown schematically at the right-hand edge of the illustration of this figure. The infeed stand 10, together with its equipment, can, however, also be used in conjunction with printing devices employing flat templates.

The material 12 to be printed upon is pulled off a suitable nonillustrated supply over further appropriate non-illustrated transport rollers and is delivered via a roller 13 to the transport band 14. A heat source, designated in its entirety by reference character 18, is arranged between a deflecting roller 15 and a pair of rollers 16 and 17. Heat source 18 consists of a plurality of adjacently arranged heat radiating elements 19 which are secured to a cover or shield 20 along the transport band 14, as shown. The cover or shield 20 is composed of, for instance, sheet metal and is pivotable about a shaft or axis 21 disposed parallel to the axes of the rolls 16, 17 of such pair of rollers, into the phantom line position 18'.

Any suitable means, such as the schematically illustrated guide arrangement 30, can be provided for enabling the roller 17 to be lowered into the phantom line position 17', whereby the transport band 14 arrives at the phantom line position 14, in other words is removed from the heating source 18. Lowering of the roller 17 and the rocking of the heat source 18 upwards can be combined with the simultaneous switching off of the heat radiating elements 19. The material 12 to be printed upon is preferably guided over the heating source 18, so that the cover or shield 20 functions as a guide and preheats the material 12. In certain instances, this material 12 to be printed upon can also be guided beneath the heating source 18, especially when processing printable material in the form of fine woven goods, the edges of which have a tendency to roll in.

With the foregoing background in mind, the operation of the apparatus depicted in FIG. 2 will now be considered and is as follows. The material 12 to be printed upon is trained about the roller 13 and is guided along the cover or shield 20 of the heating source 18 and arrives at the contact location of the roller pairs 16, 17 with the transport band 14. The cover or shield 20 of the heat radiation source 18 preferably consists of a rust-proof, curved sheet metal member, at the lower face of which there are arranged the heat radiating elements 19, for instance infrared radiating devices, which predominantly radiate their infrared heat in the direction of the transport band 14, therebycausing the thermoplastic adhesive material carried thereon to assume a tacky condition. The heat losses, which are radiated upwards in the direction of the cover member or shield 20, serve to heat the latter and therefore the material 12 at the side which is to be adhesively bonded with the transport band 14.

The preheated material 12 to be printed and the now tacky thermoplastic adhesive are collectively guided between the nip line or contact line of the rollers or the pair of rollers 16, 17 and are pressed together. Roller 16 constitutes a pressure or contact roll, which is unheated, whereas contact or pressure roll 17 can be constructed as a rubber roller.

Depending upon the desired heat intensity for achieving a desired adhesive force, it is possible to provide a suitable control device, schematically depicted at 31, in order to individually or in sections switch on or switch off the heat radiating elements 19. Further, the contact pressure of the pressure roller 16 can be regulated as a function of the speed, if desired. An arrangement suitable for this purpose is disclosed for instance in the previously mentioned U.S. Pat. No. 3,601,299.

Should the machine be stopped, then the rollers 16 and 17 are separated from one another, in that the roller 17 can be lowered via the guide arrangement 30 into the illustrated phantom line position 17', so that also the transport band 14 is dropped into the phantom line position 14. At the same time, the heat source 18 is pivoted as a unit about the axis or shaft 21 through an angle of, for instance, approximately 15 in the upward direction so as to assume the phantom line position 18'. When this occurs the previously operable heat radiating elements 19 can be switched off.

Since the heat source 18 extends over a certain length of the transport band 14 and also can be arranged between the transport band 14 and the material 12 to be printed upon, it is possible to achieve a sufficient tackiness or adhesiveness of the thermoplastic adhesive applied to the transport band 14 even with large velocities of the material to be printed. As a result, it is possible to obtain, in conjunction with the accommodation of the contact force of the pairs of rollers 16, 17 and the slight preheating of the material 12, that adherence of the material 12 to be printed with the transport band 14 which is necessary for passing through all of the printing-or coloring stations. By virtue of the accurate adjustment possibility for the dosing of the effective quantity of heat, it is additionally possible to insure that the drawing off of the material 12 from the transport band 14 can be undertaken without undue application of force and no distortion of the material occurs. When printing fine woven materials, this can be achieved because the tendency for the edges of such fine woven goods to roll in, as previously explained, can be compensated for by passing the material beneath the heating source 18. Furthermore, the lengthwise extension of the heating source brings about, even in such situation, a sufficient tackiness of the thermoplastic adhesive.

While there is shown and described present preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims.

What is claimed is:

1. Transport apparatus comprising in combination with a printing station, the improvement of a transport band, a web of material to be carried by said band without relative displacement when printed upon at said printing station, means to deliver said web of material to said transport band, said transport band having a layer of thermoplastic adhesive with only sufficient strength to hold said web without displacement during printing and then cleanly release the same whereby through application of heat and pressure said web of material can be temporarily adhesively bonded to said transport band, said web of material having sufficient strength after passing through said printing station to be cleanly pulled off said transport band, means located downstream of said printing station for so pulling said web from said transport band, a pair of rollers defining a contact location upstream of said printing station for pressing said web of material onto said transport band, heating means spaced from said transport band for directly heating said layer of thermoplastic adhesive of said transport band at the side thereof coming into contact with said web of material and arranged along a partial length of said transport band covered with said thermoplastic adhesive, said heating means being separate from and disposed in front of said pair of rollers for said web of material and said transport band, a plurality of adjacently arranged heat radiating elements directed toward said adhesive layer of said transport band, cover means for at least partially screening the heat which is radiated in the opposite direction, said web of material being guided over and in contact with said cover means for simultaneous preheating, said heat radiatin elements being supported by said cover means, an means for dlsplaceab mounting said cover means for selectively positioning said heat radiating elements together with said cover means and said web of material away from said transport band in order-to at least reduce the heating effect upon the thermoplastic adhesive layer of said transport band.

2. A screen printing machine as defined in claim 1, said heating means being arranged directly in front of said pair of rollers, and means for guiding said web of material over said heating means.

3. A screen printing machine as defined in claim 2, wherein one of said rollers of said pair of rollers is ar ranged beneath said transport band, and means cooperating with said one roller to enable lowering thereof in a direction away from said transport band.

4. A screen printing machine as defined in claim 1, wherein said mounting means comprising a shaft member for pivotably mounting said cover means, said shaft member being arranged at the region of said pair of rollers and extending in substantial parallelism to the axes of said pair of rollers. 

1. Transport apparatus comprising in combination with a printing station, the improvement of a transport band, a web of material to be carried by said band without relative displacement when printed upon at said printing station, means to deliver said web of material to said transport band, said transport band having a layer of thermoplastic adhesive with only sufficient strength to hold said web without displacement during printing and then cleanly release the same whereby through application of heat and pressure said web of material can be temporarily adhesively bonded to said transport band, said web of material having sufficient strength after passing through said printing station to be cleanly pulled off said transport band, means located downstream of said printing station for so pulling said web from said transport band, a pair of rollers defining a contact location upstream of said printing station for pressing said web of material onto said transport band, heating means spaced from said transport band for directly heating said layer of thermoplastic adhesive of said transport band at the side thereof coming into contact with said web of material and arranged along a partial length of said transport band covered with said thermoplastic adhesive, said heating means being separate from and disposed in front of said pair of rollers for said web of material and said transport band, a plurality of adjacently arranged heat radiating elements directed toward said adhesive layer of said transport band, cover means for at least partially screening the heat which is radiated in the opposite direction, said web of material being guided over and in contact with said cover means for simultaneous preheating, said heat radiating elements being supported by said cover means, and means for displaceably mounting said cover means for selectively positioning said heat radiating elements together with said cover means and said web of material away from said transport band in order to at least reduce the heating effect upon the thermoplastic adhesive layer of said transport band.
 2. A screen printing machine as defined in claim 1, said heating means being arranged directly in front of said pair of rollers, and means for guiding said web of material over said heating means.
 3. A screen printing machine as defined in claim 2, wherein one of said rollers of said pair of rollers is arranged beneath said transport band, and means cooperating with said one roller to enable lowering thereof in a direction away from said transport band.
 4. A screen printing machine as defined in claim 1, wherein said mounting means comprising a shaft member for pivotably mounting said cover means, said shaft member being arranged at the region of said pair of rollers and extending in substantial parallelism to the axes of said pair of rollers. 